1. Field of the Invention
The invention concerns a method for operating a wind power plant with a rotor-driven electric generator for delivering electric power to an electric grid which provides a grid voltage in which, when excess voltage prevails in the grid, idle power from the wind power plant is fed to the grid in order to lower the voltage.
The invention further concerns a wind power plant with a rotor-driven electric generator for delivering electric power to an electric grid in which when excess voltage prevails in the grid idle power from the wind power plant is fed to the grid in order to lower the voltage.
2. Description of Related Art
From DE 10 2004 048 339 A1, a wind power plant is known which has a rotor, a generator driven by it with a power converter for feeding electric energy via a connection to an electric supply network and a control unit, where the control unit has converter controller. Here it is envisaged that the control unit has an input connector for a reference value of the voltage to deliver, in which an additional regulator is provided on the input of which the reference voltage is applied and on the output of which idle power reference values are output and applied to the converter controller. The additional regulator is designed to calculate idle power reference values from the signal for the reference voltage, to record with the help of a sensor, the actual voltage delivered by the wind power plant and, after comparison with the reference voltage, to correct the idle power reference values. This consequently links the setting of a desired power coefficient with a voltage stabilizing method. This enables full utilization of the idle power potential of the wind power plant without occurrence of damage due to excessive increasing voltage. Furthermore, this regulator has the advantage that it enables robust operation of the wind power plant with impulse-like voltage transients.
From EP 1 386 078 B1, a wind power plant and a method for operating a wind power plant are known in which idle power from the wind power plant is fed to the electrical grid and the idle power is specified by a phase angle phi, which describes an angle between the current and the voltage of the electric power fed. Thus the phase angle determines the idle power portion of the power delivered by the wind power plant; the phase angle phi is changed dependent on the level of at least one voltage measured on the grid, with the phase angle unchanged as long as the grid voltage is between a predetermined lower reference value and a predetermined upper reference value, where the lower voltage value is smaller than a reference voltage value and the predetermined upper voltage value is greater than a predetermined reference voltage value and where if the predetermined upper voltage value is exceeded or the voltage drops below the predetermined lower voltage value, the magnitude of the phase angle increases with a further increase or reduction in voltage.